This invention relates to gas analyzers for determining constituents in a gas sample by detecting the energy loss of radiation transmitted through the gas sample.
Gas analyzers having a single chamber traversed by radiation absorbed by the gas are disclosed, for example, in U.S. Pat. No. 3,696,247, which describes such analysis of exhaust gases in motor vehicles, and in an article entitled "Pattern Recognition Logic Analyzes Infrared Signals" at page 112ff of the Nov. 11, 1968 issue of Electronics. In such gas analyzers, the radiation is repeatedly reflected by mirrors suitably disposed in the test chamber, so that it will reach the detector only after traversing a considerably greater distance through the gas than the direct distance between entrance and exit windows. As a result, the total distance traversed by the radiation through the gas may be greater than the maximum dimensions of the test chamber. This serves to increase the sensitivity of the gas analyzer without enlarging the chamber.
It is desirable to keep the chamber as small as possible since, after each measurement, the chamber must be flushed to remove gas residues and the smaller the gas volume and hence the chamber, the more quickly the flushing may be accomplished.